1. Field of the Invention
The invention relates to a scooter, i.e., a two-wheeled, one-track, muscle-powered rolling vehicle, which can be used, in particular, for recreational use, as well as for transportation in urban areas.
2. Description of the Prior Art
Scooters, in particular as they are known as a sports and recreational device for children and adults, are usually driven by pushing with one leg against the ground. Steering is undertaken by hand via a bicycle-like steering rod with a handle bar that acts exclusively on the front wheel. Because of this design, a turning circle is needed to turn the vehicle that corresponds, in normal use, to at least double the wheelbase of the vehicle. Furthermore, the rear wheel of a scooter of this type does not follow the track of the front wheel exactly, making it more difficult to deliberately avoid obstacles with an estimate of both tracks of the wheels.
The maneuverability of such a scooter could be improved by a steerable rear wheel. Scooters of this type with two steered axles are known, for example, from U.S. Pat. No. 4,799,702. Here, the displacement of the rear axle is initiated by a weight shift and the slanted position of the standing board that results. The rear wheel fork is embodied in such a way as to be pivotable around an axle vertically relative to the longitudinal direction of the vehicle. The pivoting movement is limited by a crossbar, to the ends of which are attached two helical springs. This arrangement causes a displacement of the beam against spring force and a pivot back into the rest position for straight-ahead travel. Here, the relatively inexact control of the rear directional control, which is only carried out via the feet on the standing board, is disadvantageous. The independent displacement of the two axles can result in out-of-track travel by the rear part of the scooter relative to the front part, which negatively influences straight-ahead travel. Maneuverability is only slightly increased with this type of two-axle steering.
Furthermore, a scooter is known from U.S. Pat. No. 4,555,122, whose rear wheel turning angle is dependent on the turning angle of the front wheel. This forced steering avoids some of the disadvantages of independent rear wheel guidance. However, in this design, which has a rod coupling of the two forks, the relatively imprecise directional control of the rear wheel is disadvantageous. Depending on the turning angle, the rear wheel runs more or less out of the track of the front wheel. In the case of a small turning angle, the turn of the rear wheel follows that of the front wheel rather exactly. In the case of a stronger turn of the front wheel, however, the turn of the rear wheel again becomes increasingly smaller. In addition, the two forks of this scooter are exactly vertical, i.e., the steering axles are parallel to the vertical axle of the scooter. This causes relatively unfavorable driving performance with respect to straight-ahead travel and maneuverability, because there is no after-running of the wheels. Furthermore, it is only conditionally possible to generate forward drive by means of a swinging body motion and thus a serpentine motion of travel.
Finally, U.S. Pat. No. 3,620,547 discloses a scooter with steerable front and rear wheels. The front wheel is turned in a conventional fashion via a handle bar, while the rear wheel is independently turnable. As a result, both parallel turning angles ("crab steering") and turning angles in opposite directions are possible. Without explaining further, the aforementioned patent speaks of positive steering of the rear wheel, dependent on the angle of turn of the front wheel. Whether this steering is carried out with the help of a belt, a chain or perhaps a rod linkage is not specified.
Moreover, a bicycle with conventional pedal drive is known from German reference DE 37 27 771 A1. The driven front wheel is connected rigidly, i.e., in non-steered fashion, to the frame. Steering is provided by a smaller rear wheel. The transmission of the steering movement from the steering rod to the rear wheel is carried out essentially by an endless drive, such as a chain, knob or toothed belt or steel cable. The transmission of power from the rotatable axles, namely, the steering rod and the rear wheel fork, to the endless drive is carried out by driving and output gears, which are connected in rotation-proof fashion to the axles and around which the endless drive is placed. This type of power transmission, however, cannot simply be transferred to scooters.
Furthermore, in all of the aforementioned scooters, which constitute the prior art, it is necessary, in order to maintain a certain speed on a level surface, to repeatedly push one's leg against the ground.